Hydraulic press equipped with a synchronized stripping plunger



W. ERNST ET AL HYDRAULIC PRESS EQUIPPED WITH A SYNCHRONIZED STRIPPINGPLUNGER Filed June 5, 1944 INVENTOR WALTER ERNST BY cums Mining/4ATTORNEY Patented a. is, 1949 HYDRAULIC PRESS EQUIPPED WITH ASYNCHBONIZED S'I'BIPPING'PLUNGEB Walter Ernst and Clyde Hedriek, MountGilead, Ohio, assignors to H-P-M Development Corporation, Wilmington,Del., a. corporation of Delaware Application June 5, 1944; Serial No.538,879

This invention relates to hydraulic apparatus and, in particular, tohydraulic drawing presses and the like.

In the drawing of sheet metal and similar operations it is oftennecessary forcibly to re; move the formed workpiece from the punch ordie within which it has been shaped. Most often, it is necessary toremove the workpiece from a male die or punch portion carried by themovable platen of the drawing press. To accomplish the stripping oif ofthe workpiece, a plunger is provided which is urged downwardly throughthe punch and into engagement with the workpiece thereon.

This invention has for its primary object the provision of an actuatingsystem for such a plunger which synchronizes the action thereof with themovement of the press platen.

It is another object to provide in a hydraulic press a hydraulicallyactuated stripping plunger and an auxiliary hydraulic circuit therefor.

These and other objects will become more apparent upon reference to thefollowing specification and the accompanying drawings, in which:

Figure l is a diagrammatic view of a hydraulic press having an auxiliaryplunger actuated by a hydraulic system according to this invention; and

Figure 2 is a diagrammatic wiring diagram showing the electrical circuitassociated with the auxiliary plunger actuating system.

General arrangement In general, a reciprocable ram is supplied withactuating fluid from any suitable hydraulic circuit such as a reversiblepump.

The ram is adaptedto reciprocate a die member to form a workpiece. Theram is bored to receive a plunger which is reciprocable within the saidbore and is adapted to eject the workpiece from the die member carriedby the said ram.

The ejecting or stripping plunger is preferably double acting andhas itsretraction area connected with the retraction area of the main ram. Theadvancing side of the stripping plunger 11 Claims. (01. 11

I taneously with the commencing of the retraction I of the cylinder l0through the conduit 18.

of the main ram and pressing member carried thereby.

Preferably, the main press ram is controlled by electrical devices whichare interlocked with elecq trical control means for the strippingplunger so that the actuation of the former is automatically operable toactuate the latter.

Structural arrangement Referring to Figure 1, there is shown a drawingpress comprising a main cylinder ill within which is reciprocable thedifferential plunger ii. The plunger H has attached thereto a platen I!which is adapted to carry a pressing member (not shown).

The diiferential plunger H defines with the cylinder l0 advancing andretracting chambers which are supplied with actuating fluid from a pumpI3 through the conduits ii and I5 respectively. The conduit I5 isconnected by a conduit I6 with the inwardly opening check valve I?located within the reservoir or tank l8. Mounted in the top of thecylinder 10 is a surge valve IQ of any suitable construction, the surgevalve being actuated by fluid conducted thereto by the conduit 20which-is connected with the conduit 16. Also mounted within the tank I8is a valve 21 which is hydraulically connected with the advancingchamber of the cylinder it by a conduit 22 and with the retractionchamber The valve 2| is operable at the moment of reversal is suppliedwith pressure fluid from an auxiliary '24 to which is fastened thesolenoid SI.

of the plunger H at the end of a working stroke to bypass the deliveryof the pump I3 while simultaneously releasing the pressure from theadclockwise, and places the pump in position to deliver into the conduitIS. The arm 24 is also adapted to be engaged by the rod 25 attached tothe platen 12 so that the pump 13 is automati-- cally moved to nodelivery position thereby when the platen l2 and plunger H are in theirretracted position. a

The plunger ii is bored as at 30 to receive the double acting plunger 3|the latter being reciprocable through a bore in the platen [2 so as toengage the workpiece or the ejector pins of the pressing member carriedby the said platen. The retraction area of the plunger 3| is connectedthrough a bore 32 with the retraction area of the plunger H. The bore 32includes an adjustable restrictor 33 which may comprise a needle valveor any other suitable type of choke valve. The advancing area of theplunger 3| is connected by a bore 34 in the plunger H with a conduit 35which is adapted to supply actuating fluid to the said plunger.

Actuating fluid for the plunger 3| is supplied by a pump 36 which isconnected to the four-way valve 31. The pump 36 is preferably a one-waydelivery type pump and continuously draws fluid from the reservoir l8and discharges the same into the valve 31. The valve 31 is provided withthe pilot cylinders 38 and 39 which are connected,

respectively, by the conduits 40 and 4| with the service ports of afour-way valve 42. The fourway valve 42 is adapted to be shifted intoone end position by a spring 43 and, into the other end position by asolenoid S4 when the latter is energized. Pressure fluid may be suppliedto the four-way valve 42 in any suitable manner such as by the pump 44.

The valve 31 comprises a pair of service ports one of which is connectedby the conduit 45 through the check valve 46 with the advancing chamberof the cylinder Ill. The valve 46 is eifective to permit flow into thesaid advancing chamber but not therefrom. The other service port of thevalve 31 is connected by a conduit 41 to the inlets of the valves 48, 49and 50, the outlets of these valves being connected to the conduit 35.The valve 48 is a check valve which permits free flow of fluid from theconduit 41 to the conduit 35 but not vice-versa. The valve 49 is a chokevalve adapted to create a predetermined restriction from the flow offluid from the conduit 35 to conduit 41 and the valve 50 is a pressurerelief valve adapted to relieve the pressure in the conduit 35 shouldthe same exceed a predetermined amount.

The solenoid S4 is adapted to be energized by a contactor blade S3Awhich is associated with the solenoid S3. When the solenoid S3 isenerized, the aforementioned contactor blades indicated at 83A closesand the solenoid S4 is energized to shift the valve 42.

- Located in the press frame or in association with the platen l2 so asto be contacted thereby are a plurality of limit switches LSI, LS2, LS3and LS4. LS2 is a normally open switch which is momentarily closedduring the retraction stroke when the said pressure has attained apredetermined value.

Referring to Figure 2 the arrangement of the limit switches andsolenoids in the rectrical circult is shown. In Figure 2 the supplylines are indicated at 5| and 5|. Connected to the line 5| is acontactor solenoid indicated at C which is connected at its other end toa switch 52 which in turn is connected with a push button 53. The pushbutton 53 is connected to a junction point 54, the junction point beingconnected through a normally closed push button 55 and a normally closedtemperature responsive switch 56 with the line 5|. The switch 52 is anormally open push button station having means associated therewith forlocking t1; switch in a closed position.

Also connected with the line 5| are the solenoids SI and S2 which areconnected at their other ends. with the limit switch LS4 which latterconnects through the normally closed blade Tl of the switch T, thenormally open limit switch LS3 and the normally open blade CI of thecontactor solenoid C with the junction point 54. A blade SIA of thesolenoid S| is arranged to bypass the limit switch LS3 and the contactorblade CI.

Also connected with the line 5| is the solenoid S3 which has connectedto its other end the partil of the press platen. The limit switch LS2 isconnected in parallel with a pair of contacts which have associatedtherewith ablade which is actuated by a solenoid S2. The solenoid S2 isadapted, when energized, to open the contacts and when deenergized topermit the said blade to close the contacts. The limit switch LSI is anormally closed switch which is positioned so as to be opened when theplunger II has completed its retraction stroke. The limit switch LS3 isa normally open switch which is adapted to be closed by the platen whenthe latter is in its fully retracted position and the switch LS4 is anormally closed switch adapted to be opened by the platen at the end ofthe working stroke of the press.

' A pressure responsive switch T is hydraulically connected with theconduit l4 so as to be actuated byvthe working pressure on the plungeralleled limit switch LS2 and the blade 82A of the solenoid S2. The bladeS2A and the limit switch LS2 are connected together and thence throughthe limit switch LSI are connected with the junction point 54. Thesolenoid S3 is adapted to close the blade 83A to complete a circuit fromthe line 5| through the valve solenoid S4 to the line 5|. A wire 51connects from between the switches 52 and 53 to a point between theswitch LS3 and the blade CI for a purpose which will become moreapparent hereinafter.

Operation Assume that the press occupies the position shown in Figure 1,that is, with the plunger fully retracted. A working stroke of the pressis instituted by energizing the solenoid S| by depressing the startbutton 53. Closure of the button 53 completes a circuit through thesolenoid S| through the limit switch LS4, the pressure switch Tl, thelimit switch LS3, the push button 53, the reverse button 55 and thetemperature switch 56 to the line 5|. When the solenoid SI is energizedthe blades SI A close and thus establish a holding circuit permittingthe push button 53 to be released.

Simultaneously with the energization of the solenoid S|,'the solenoid S2is energized and opens the blades S2A. However, since the limit switchLSI serially connected with the blades SZA was previously opened by theplaten, the energization of the solenoid S2 is not immediatelyefiective.

After the press platen has advanced into and accomplished the work to bedone thereby, the solenoid SI is deenergized either through actuation ofthe pressure switch 'I', the actuation of the limit switch LS4 or theactuation of the push button switch- 55, and the pump |3 shifts todirect fluid to the retraction chamber of the cylinder l0.Simultaneously with the deenergization of the solenoid SI, the solenoidS2 is deenergized thereby permittin the blade 82A to close. Closure ofthe blade S2A establishes a circuit through the solenoid S3, and thelimit switch LSI to the junction point 54 and thence through theswitches 55 and 55 to the line 5|.

Energization of the solenoid S3 closes the blade 83A and energizes thevalve solenoid S4 so as to shift the valve 42. The shifting of the valve42 directs pilot fluid from the pump 44 through the conduit 40 to thepilot cylinder 38 thus shifting the valve 31 to direct pressure fluidfrom the pump 36 to the conduit 41; The pressure fluid delivered to theconduit 41 passes through the check valve 48 and the conduit 35 into thpassage and thence to the advancing area of the plunger 3|. Thus,substantially simultaneously with the deenergization of the solenoid SI,actuating fluid is conducted to the advancing side of the strip pingplunger 3|.

.valve 2| while simultaneously relieving the pressure in the advancingchamber through the conduit 22 and the valve 2 I. After a predeterminedreduction of the pressure in the advancing chamher, the aforementionedbypass is closed off and the retraction stroke of the plunger Ii com--stripping is thus accomplished without any delay.

The limit switch LS2, which is connected in parallel with the blade SZA,is adapted to energize the solenoid S3 during the retraction stroke ofthe platen l2 should it be desired to accomplish the stripping of theworkpiece in this manner. It will be apparent, however, that the delayin the actuation of the plunger when the same is controlled by the limitswitch LS2, is suflicient to permit the platen l2 to be retracted fromthe stationary die member so that the workpiece, when ejected, is likelyto fall through a distance which may be sufiicient to produce harmfuleffects. Accordingly, it is preferable to actuate the stripping plungerby means-of the solenoid S2 and the contact blade SZA. I

During the retraction stroke of the plunger l I, the stripping plunger3| is in its lower position. When the platen reaches its uppermostposition a cam carried by the platen engages and opens the limit switchLSI thus deenergizing the solenoid S3. Deenergization of the solenoid S3permits the blade S3A to open thus deenergizing the solenoid S4. Withthe solenoid S4 deenergized the spring 43 shifts the valve 42 to directpilot fluid through the conduit 4| to the pilot cylinder 39 of the valve37, shifting the latter to direct the discharge from pump 36 through theconduit 45 and into the advancing chamber of the cylinder Ill. The fluidthus directed to the said advancing chamber is discharged, when thepress stands idle, through the surge valve i9 and into the tank l8.Shifting of the valve 37 also connects the conduit 41 with the inletside of the pump 36 whereupon fluid within the chamber above thestripping plunger 3| is withdrawn slowly through the conduit and thechoke valve 49 to retract the stripping plunger within the main 6plunger. The space below the stripping plunger receives liquid uponretraction of the plunger by way of the choke l3. passage 32 and theretracting area of the main plunger.

During the advancing stroke of the plunger l I the discharge from thepump 36 is effective to augment the speed of advance ,of the plunger ll.

Full automatic cycling of the press may be had by locking the button I2closed. This energizes contactor solenoid C and closes the blades CI.The, when the press platen reaches its Figure 1 position and closes thelimit switch LS3, the solenoids SI and S2 are automatically re-energizedto commence another advancing stroke of the platen.

It will be apparent that various modifications may be made in thestructural arrangement of this invention without in any way departingfrom the spirit of the invention, and, accordingly, it is desired tocomprehend such modifications as may be considered to come within thescope of the appended claims and the invention.

Having thus fully described our invention, what we claim as new anddesire to secure by Letters Patent is: a

1. In combination in a drawing press, a fluid operable drawing plunger,a fluid operable ejector plunger, a source of pressure fluid forsupplying actuating fluid to said drawing plunger, a first control meanseffective when actuated to bring about the advancing stroke of saiddrawin plunger, a source of pressure fluid for supplyin actuating fluidto said ejector means, a second control means effective when actuated tobring about the advancing strokeof said ejector plunger, meansinterlocking said control means to prevent the actuation of the secondthereof when the first thereof is actuated, and means responsive to apredetermined advancing movement of said drawing plunger forsimultaneously rendering ineffective said first control means and foractuating said second control means.

2. In combination in a hydraulic press, a drawing plunger having fluidoperable advancing and retracting means associated therewith, anauxiliary ejector plunger carried by said drawing plunger and havingfluid operable advancing and retracting means associated therewith,means hydraulically connecting the retracting means of said drawingplunger with the retracting means of said ejector plunger, a reversiblepump connected with said'drawing plunger for Supplying actuatin fluidthereto, means continuously urging said pump into position to deliver tosaid retracting means of said plunger, electrical means effective whenenergized to position said pump to deliver to said advancing means ofsaid drawing plunger, an auxiliary fluid source connected with theadvancing means of said ejector plunger, electrical control meanseffective when energized to permit the supply of fluid from said fluidsource to said ejector plunger, an electrical circuit connected vwithsaid flrst mentioned electrical means and adapted selectively to beenergized to bring about the advancing stroke of said drawing plunger, asecond electrical circuit connected with said second mentionedelectrical means adapted when energized to bring about the advancingstroke of said ejector plunger, and means including a contactorconnected in parallel with said first mentioned electrical means forpermitting the energization of said second mentioned electrical meanssimultaneously with the deenergization of said first mentionedelectrical means.

3. In combination in a drawing press, a drawing plunger having fluidoperable advancing and retracting areas associated therewith, areversible pump connected with said areas and selectively operable tosupply actuating fluid to one or the other, means normally positioningsaid pump to deliver to said retracting area and a solenoid adapted whenenergized to position said pump to deliver to said advancing area, abore in said plunger, a reciprocable ejector plunger mounted in saidbore and having fluid operable advancing and retracting areas associatedtherewith, an adjustable choke valve having its inlet connected with theretracting area of said drawing plunger and its outlet connected withthe retracting area of said ejector plunger, a fluid source connectedwith the advancing area of said ejector plunger for supplying actuatingfluid thereto, valvemeans connected with said fluid source and saidejector plunger and normally positioned to exhaust said ejector plunger,electrical actuating means for actuating said valve to bring about thesupply of fluid from said fluid source to said ejector plunger advancingmeans, means for energizing said solenoid to bring about the advancingmovement of said drawing plunger, means parallelly connected with saidsolenoid and operable when energized to prevent the energization of saidelectrical actuatin means, means for deenergizing said solenoid at theconclusion of the working stroke of said drawing plunger, means operablesimultaneously therewith for energizing said electrical actuating means,and means operable at the conclusion of the retraction stroke of saiddrawing plunger for deenergizing said electrical actuating means.

4. In combination in a drawing press, a fluid operable drawing plunger,a fluid operable ejector plunger carried by said drawing plunger,a-first source of pressure fluid for supplying actuating fluid to saiddrawing plunger, a first electrical control means effective whenenergized to bring about the advancing stroke of said drawing plunger, asecond source of pressure fluid for supplying actuating fluid to saidejector plunger, a second electrical control means efiective whenenergized to bring about the advancing stroke of said ejector plunger,means selectively operable for energizing said first control means, acontactor having a normally closed blade serially connected with saidsecond control means con- 4 nected with said first control means so asto be energized simultaneously therewith, means operable at theconclusion of the working stroke of said drawing plunger fordeenergizing said first control means and also said contactor, thedeenergization of said contactor being adapted to bring about theenergization of said second con- 'trol means, and means including anormally closed limit switch serially connected with said second controlmeans for bringing about the deenergization thereof when said drawingplunger has completed its retraction stroke.

5. In combination in a drawing press, a double acting drawing plunger, adouble acting ejector plunger carried thereby, a first source ofpressure fluid connected with said drawing plunger for supplyingactuating fluid thereto, a first electrical control means adapted whenenergized to bring about the supply of fluid from said first fluidsource to the-advancing side of said drawin pl n r, means including anadjustable choke valve hydraulically connecting the retracting side ofsaid drawing plunger wtih the retracting side of said ejector plunger, asecond source of pressure fluid for supplying actuating fluid to theadvancing side of said ejector plunger, a second electrical controlmeans effective when energized to permit the supply of pressure fluidfrom said second source to the advancing side of said ejector plunger,an adjustable choke valve serially arranged between said second sourceand said ejector plunger, means for energizing said first control meansto bring about the working stroke of said drawing plunger, meansoperable at the conclusion of said working stroke for deenergizing saidfirst control means to bring about the retracting stroke of said drawingplunger, and electrical means associated with said second control meansfor preventing the energization thereof during the advancing stroke ofsaid drawing plunger or when said drawing plunger is in its retractedposition.

6. An electrical control system for controlling the movements of adrawing plunger and an ejector plunger in a drawing press whichcomprises a first electrical means adapted when energized to bring aboutthe working stroke of said drawing plunger, a second electrical controlmeans adapted when energized to bring about the ejecting stroke of saidejector plunger, a contactor adapted when deenergized to permit theenergization of said second control means and when energized to preventthe energization of said second control means, said contactor beingadapted to be energized and deenergized simultaneously with said firstcontrol means, whereby the deenergization of said first control means atthe end of a working stroke of said drawing plunger is efiectivesubstantially instantaneously to permit the energization of said secondcontrol means.

7. In combination, first and second double acting plungers, fluidpressure supply means for said plungers, first control means for saidfirst plunger movable into a first and a second position for bringingabout a supply of fluid to said first plunger in its advancing andretracting movements, respectively, second control means for said secondplunger movable into a first and a second position for bringing aboutthe supply of fluid to the advancing area of said second plunger or forexhausting said advancing area, respectively, yielding meanscontinuously urging said control means toward their second positions,first and second electrical means energizable for moving said first andsecond control means, respectively, into their first positions, otherelectrical means energizable simultaneously with said first electricalmeans for interrupting the circuit to said second electrical means andde-energizable simultaneously with said first electrical means toreestablish the circuit to said second electrical means, and switchmeans responsive-to the movement of said first plunger into its fullyretracted position for interrupting the circuit to said'secondelectrical means.

8. In-a drawing press having a drawing plunger and an ejector plunger, afirst electrical means energizable to bring about the working stroke ofsaid drawing plunger and de-energizable to bring about the retractingstroke of said drawing plung-' er, a second electrical means energizableto bring about the ejecting stroke of said ejector plunger andde-energizable to bring about the retracting stroke of said ejectorplunger, normally closed switch means in circuit with said secondelectrical means, means connected in parallel with said first electricalmeans and operable when energized to open said switch means, and otherswitch means in circuit with said second electrical means and positionedto be opened by said drawing plunger in its fully retracted position.

9. In combination in a drawing press, a drawing plunger and an ejectorplunger each having advancing and retracting means, first electricalmeans energizable to bring about a supply of fluid to the advancingmeans of said drawing plunger and de-energizable to bring about a supplyof fluid to the retracting means of said drawing plunger, secondelectrical means energizable to bring about a supply of fluid to theadvancing means of said ejector plunger and de-energizable to bringabout the exhaust of the advancing means thereof, a circuit interlockingsaid electrical means whereby the de-energization oi the first thereofsubstantially instantaneously energizes the second thereof, switch meansactuated by said drawing plunger in its fully retracted position forde-energizing said second electrical means, and'channel means connectingthe retracting means 01' said plungers.

10. In combination in a drawing press, a drawing plunger and an ejectorplunger each having advancing and retracting means, first electricalmeans energizable to bring about a supply of fluid to the advancingmeans of said drawing plunger and de-energizable to bring about a supplyof fluid to the retracting means of said drawing plunger, secondelectrical means energizable to bring about a supply of fluid to theadvancing 11. In combination in a drawing press, a draw ing plunger andan ejector plunger each having advancing and retracting means, firstelectrical means energizable to bring about a supply of fluid to theadvancingmeans of said drawing plunger and de-energizable to bring abouta supply of fluid to the retracting means of said drawing plunger,second electrical means energizable to means, restricted channel meansconnecting the means of said ejector plunger and de-energizableretracting means of said plungers, and means restricting the exhaust offluid from the advancing side of said ejector plunger,

WALTER ERNST. CLYDE HEDRICK.

narnaancas crran The following references are of record in the file ofthis patent:

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